Hello
Can anyone explain or send me to an explanation of how to use the scale on the focusing knob of the Sinar F2. Will it help me focus better and give me best aperture to use?
JNight
Hello
Can anyone explain or send me to an explanation of how to use the scale on the focusing knob of the Sinar F2. Will it help me focus better and give me best aperture to use?
JNight
If you can read french :
http://www.galerie-photo.com/mise_au...eme-sinar.html
... and if you cannot read french:
Set the focus on the most distant point which you want sharp in the picture. Turn the movable scale so that the arrow where it says 4x5" points to the white dot.
Now you focus on the closest point. Read the aperture which you set on the lens.
Important: Now you should set the focus plane in between these two readings. You simply turn the focusing knob back two f/stops.
An example: You focus on the farthest object and zero the scale. After focusing on the closest object to get everything you want in focus the indicator says f/22. Now you turn the focusing knob so that the scale points on f/11. Note that you should still set the aperture to f/22.
It is also good to know that if you work closer to or in the macro range, the indicator is off. I take it you know about the bellows draw factor, which quickly comes into play when shooting large format. It says that you have to give the film 2 more stops of exposure if you are shooting 1:1.
So what is the good news about the indicator being off in macro range. Well, the indicator is off by exactly the same factor as the bellows draw factor. I.e. if the indicator says that you should use f/45 it actually means f/22 at 1:1. But you should not compensate for this when you set the plane of focus, only when you set the aperture. (And yes, two stops of exposure gained is often something to be happy about, especially when shooting at small apertures and long exposure times.)
Well
thank you for that I'll go and try it out.
JNight
Hello Bjorn
Thank you for your help so far. I tried what you told me and yes it seems to work. The place of focus after turning 2 stops back seems to place the plane of focus somewhere around 1/3 into scene would you say? This would seem to be correct. This would help greatly if there is nothing at this distance to focus on.
Also, if the aperture it suggests is at the top of your lens' capability would you continue with it and risk defraction or would you take the distant focus a bit nearer to reduce the range? My 90mm lens' narrowest aperture is F45 and I wonder whether I shouldn't use it beyond F22 to get best part of lens. I am doing some cathedral photography shortly and would like to get the best focusing possible.
Also what does the knob on the left do?
JNight
Hi!
The answer to the defraction question is "it depends". You are correct about the "limit" of f/22, but if you must use f/32 then you must. f/45 with a 90mm lens seem like you are doing something wrong anyhow.
Now to the juicy bits. The knob on the left is your swing/tilt scale. It is described in the french link above, which is still useable because of the pictures. Try some mocked up still lifes and practice. There should also be plenty of general information on how to use swings and tilts on other places on this site and others. Learning to use these controls will also often solve the problem with small apertures.
Björn
(Btw, I've been trying to figure out what the text says on the french page linked above, as the second part where he sets the DOF seems wrong. I'm about to write the author a mail about this. But the first part is OK.)
Unless you are making huge enlargements don't worry about diffraction. But I agree, f45 on a 90mm seems strange to me.
You might be interested in the rationale behind the Sinar F2 scale. It is actually just a distance scale for movement along the rail, but translated into f-stops. It automates the so-called near far method of focusing and determining the f-stop. To this end, you measure the distance in mm along the rail between where the far point focuses and where the near point focuses. (The knob is geared relative to the rail to magnify such distances.) That is called the focus spread. You then focus halfway between the two settings and use a simple formula to determine the appropriate f-stop: divide the focus spread by twice the assumed maximal allowable circle of confusion to get the f-stop. If you choose a coc of diameter 0.1 mm, that amounts to multiplying the focus spread by 10 and dividing by 2.
The whole method depends on a choice of coc and it ignores diffraction. If you want to use a different coc, you have to adjust correspondingly. If you want to balance diffraction and defocus, you should determine the f-stop by a somewhat more complicated rule. Many people use the method due to Hansma which is described elsewhere at this website. You can also look at my essay
http://www.math.northwestern.edu/~le.../dof_essay.pdf
where I discuss the method in more detail.
> But I agree, f45 on a 90mm seems strange to me.
Sometimes movements will not help with a near-far composition because the background fills the frame. These are small stones, so I was really close, and it is a HUGE tree, so I had to use a 65mm at f45. I did take some hit from diffraction.
It is hard to see on the WWW version, but on the print you can read the headstones and see that each has a Department of Corrections number. This is Lone Oak Cemetery next to the Mississippi in Southern Louisiana, a cemetery for prisoners who die behind the walls and have no family.
Ed Richards
http://www.epr-art.com
i believe the scale is only correct when the objects being focused on correspond to the heavy dashed horiz or vert lines on the ground glass.
Posting Permissions
Reply With Quote
Bookmarks